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1 Research Centre for Early Origins of Adult Disease, School of Paediatrics & Reproductive Health, University of Adelaide, Adelaide, South Australia, Australia
2 School of Women's and Infant's Health, The University of Western Australia, Perth, Western Australia, Australia
3 School of Women's and Infant's Health, The University of Western Australia, Perth, Western Australia, Australia; Women and Infants Research Foundation of Western Australia, Perth, Western Australia, Australia
4 Canadian Institutes of Health Research Group in Fetal and Neonatal Health and Development, Departments of Physiology and Obstetr, University of Toronto, Toronto, Canada
* To whom correspondence should be addressed. E-mail: kathy.gatford{at}adelaide.edu.au.
Exposure to synthetic glucocorticoids in utero markedly improves survival after pre-term birth, but repeated exposures impair fetal and postnatal growth and are associated with evidence of insulin resistance in later life. The insulin-like growth factor (IGF) axis is an important regulator of growth and metabolism before and after birth. We have therefore investigated the effects of repeated maternal betamethasone injections on plasma IGF-I, IGF-II and IGF-binding proteins (IGFBP) in fetal and postnatal progeny in the sheep. Pregnant sheep carrying male fetuses were injected with saline or betamethasone at 104, 111 and 118 days of gestation (dG, term ~ 150 dG). Plasma samples were collected at post-mortem from fetuses prior to (75, 84, 101 dG), or after one (109 dG), two (116 dG), or three (121-122, 132-133, 145-147 dG) doses of saline or betamethasone and from progeny at 42 and 84 days of age (d). Fetal weight was reduced after two or more maternal betamethasone injections, and this effect persisted to term. Repeated betamethasone exposures reduced plasma IGF-I and total IGFBP in fetuses at 133 dG and progeny at 84 d, and reduced plasma IGFBP-3 at 84 d. Fetal plasma IGF-II tended to increase transiently at 109 dG following the first betamethasone injection. Fetal, placental and/or postnatal weights correlated positively with concomitant plasma IGF-I, IGF-II and total IGFBP. We conclude that repeated exposure to synthetic glucocorticoids in utero programs the IGF axis before and after birth, which may contribute to the adverse effects of betamethasone exposure on growth and metabolism.
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